1-30-2008 Lecture 11 - -The energy carried by each photon...

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Power: the rate at which energy is used/emitted. It is measured in units called watts. o 1 watt = 1 joule per second A 100 watt light bulb radiates 100 joules of energy every second. 4 ways in which light can interact with matter 1. Emission – matter releases energy as light 2. Absorption – matter takes energy from light 3. Transmission – matter allows light to pass through it 4. Reflection – matter repels light in another direction Properties of Light Light is a vibration in an electromagnetic field through which energy is transported. Dual nature Light as a wave f λ = c (f = frequency, λ = wavelength) Light as a particle E = h f (photon, h = Planck’s constant) Light as a wave - For a wave, its speed: s = f λ - But the speed of light is a constant, c - For light f λ = c - The higher f is, the smaller λ is, and vice versa. - Our eyes recognize f or λ as color. Light as a particle - Light can also be treated as photons – packets of energy
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Unformatted text preview: -The energy carried by each photon depends on its frequency (color) o E = h f = h c / λ o Bluer light carries more energy per photon. Light and Matter-We can separate light into its different wavelengths (spectrum).-By studying the spectrum of an object, we can learn its: o Temperature o Composition o Velocity-Each atom has specific energy levels particular to that element.-Elements/molecules have specific “fingerprints” which enable us to determine composition. Electron orbits-Ground state, Excited state, Ionization Electron energy levels-Electrons cannot have just any energy while orbiting the nucleus.-Only certain energy values are allowed.-Electrons may only gain or lose certain specific amounts of energy.-Each element (atom or ion) has its own distinctive set or pattern of energy levels....
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